Chronograph Accuracy

[zeroveez]

Can anybody give me any information concerning the path length between the sensors on a CED chronograph and measurement accuracy? The CED has the facility to measure muzzle velocity with the sensors either 2, 4, 6, or 8 feet apart. Intuitively one suspects that the greater the path length involved in the measurement, the better the accuracy. Is there any data?

[rox]

Intuitively one suspects that the greater the path length involved in the measurement, the better the accuracy. Is there any data?

That is certainly the case for the Oehler 35P, which quotes the following errors for different separations at 3000 fps:

1' : 16 fps
2' : 8 fps
4' : 4 fps
8' : 2 fps

..

[zeroveez]

Very interesting; I can understand the theoretical advantage of the increase in spacing of the sensors. However, in a telephone conversation with the US manufacturer today, he tells me that this feature is no longer available with their CED chronograph. Furthermore their website shows details of two sets of sensors placed together on the same beam, one set two feet apart and the other six feet apart, the data showing very little difference between the two measurements. I have built an eight foot beam to accomodate my sensors, so I will endeavour to persevere.